The invention is directed to a structure enabling the rapid and simple adjustment of the operating capacity of a piston-type pump, for example pumps employed in the delivery of lubricant from a supply to a point of usage.
It will be appreciated that in the utilization of a piston-type pump as a lubrication delivery mechanism, it often becomes desirable to effect an adjustment of the amount of fluid discharged by the pump at each piston stroke, both for effecting changes in the volume of lubricant delivered to a specific mechanism as well as to enable adjustment of the pump for different types of mechanisms, thereby rendering the pump substantially universal in application.
Provisions have been made in prior pumps of this general type to achieve at least some degree of variation in the pump output.
Where the displacement piston of such a pump is actuated by hydraulic or pneumatic means, i.e. a pneumatic or hydraulic piston operatively connected to the displacement piston, the stroke adjustment may be achieved by the utilization of an adjustable stop which will physically limit the travel of the displacement piston during its pump stroke. The adjustable stop may, for example, be merely a simple threaded screw disposed in the path of the piston with the position of the free internal end of the adjustment screw thus determining the end of the piston travel. While this may be acceptable for a pneumatic or hydraulic structure, wherein the piston can be stopped at an intermediate point of its maximum stroke, where a mechanical drive is employed such as a "swash plate", or other mechanical linkage, the piston movement cannot conveniently be stopped at an intermediate point, and a more elaborate arrangement must be employed to adjust the volume to be delivered. In such case, adjustment can be effected by substitution of one swash plate for another but this change involves at least a partial dismantling of the pump structure. Another solution has involved the adjustment of the position of the cylinder, in which the displacement piston of the pump is reciprocable, so that the amount of operative travel of the piston in the cylinder can be varied thus adjusting the effective pump stroke.